The relationship between upper-ocean variability and the Madden-Julian Oscillation in extended-range simulations

The relationship between upper-ocean variability and the Madden-Julian Oscillation in extended-range simulations is examined using the Navy's noil-hydrostatic COAMPS regional modeling system in a two-way coupled mode for the Dynamics of the Madden Julian Oscillation field experiment period (DYNAMO) during November to December 2011. Results show the simulation better captures the initiation, propagation and characteristics of the MJOs when the model horizontal resolution is increased from 45 km to 27 km. Variation of SST in time is in phase with surface heat flux, in which SST warms (cools) during the suppressed (active) phase through strong downward (upward) heat flux. Barrier layers that exist during the suppressed phase and erod during the active phase are consistent between the observation and the 27-km run. The extended-range simulations simulate the propagation of oceanic dowuwelling equatorial Rossby waves, which provide favorable conditions for convective activity for initiation of the MJO. The model simulations are also able to capture the diurnal warming during the suppressed phase.